The present invention relates to a powder inhaler and a method of constructing the same.
A number of powder inhalers are known which use different systems for introducing a dose of powder into an air stream. Typically, the powder is inhaled into the lungs of a patient in order to treat, for example, asthma.
One such powder inhaler is disclosed in EP-A-0237507. This inhaler comprises an inhalation channel and a mouthpiece comprising an air chamber and an outlet nozzle, which together define a flow path through which a stream of air is drawn during inhalation by a user. This inhaler further comprises means for introducing powder into the inhalation channel. During inhalation, air is first drawn into and through the inhalation channel so as to pick up powder. The stream of air containing powder is then drawn through the air chamber and out of the outlet nozzle of the mouthpiece.
Powder inhalers are, however, particularly susceptible to the effects of moisture and should therefore include a desiccant, such as silica gel, to absorb any moisture. It will of course be appreciated that it is a requirement that the desiccant be contained entirely separate from the powder to be inhaled so as to avoid contamination of the powder.
In powder inhalers of the kind which comprise an inhaler body and a grip portion at one end thereof, which grip portion is rotatable relative to the inhaler body so as to provide a dose of powder for inhalation, it has been proposed to provide a chamber in the grip portion for containing desiccant. In one proposed construction the grip portion comprises first and second parts which fit together to define a chamber; the first and second parts having cooperating splines to lock the same in the rotational sense. There is, however, one major drawback with this proposed construction in that, when fitting together the first and second parts, particles of desiccant may become lodged between the splines and prevent correct assembly.
It is thus an aim of the present invention to provide a powder inhaler having a construction which allows the parts thereof that define the chamber for containing desiccant to be fitted in a sure and reliable manner when enclosing desiccant.